Separation of gas mixtures can be necessary for a variety of reasons. In some processes, the products are produced as a mixture of gases, e.g., the separation of ethylene from a refinery gas stream for the production of polyethylene. In other processes, a waste stream must be treated to remove environmental pollutants before the stream can be released. In another example, volatile solvents can be recovered for reuse in a process by separating the solvent vapors from an exhaust stream. In another example, greenhouse gas emissions from power plants can be eliminated by separating carbon dioxide (CO2) from the flue gas and providing a pure stream of CO2 that is suitable for sequestration.
Current separation processes are inefficient and expensive. For example, pressure swing processes have the disadvantage of high cost due to the need to raise and lower the process gas stream pressure. Temperature swing processes have the disadvantage that efficient heating and cooling of the sorbent can be difficult because high surface area solids generally have poor heat transfer properties.